1. Field of the Invention
The present invention relates to a method for fabricating a semiconductor device, and in particular a method for fabricating a semiconductor device provided with interconnections or electrodes having high reliability. The present invention also relates to a method for producing interconnections, electrodes and insulating films which are of high density and firmly adhered to an underlying layer.
2. Description of the Prior Art
Metal films for forming interconnections or electrodes and insulating films for semiconductor devices have been deposited through a variety of methods such as the vacuum evaporation method, sputtering method and CVD method under a reduced pressure or atmospheric pressure. Such metal films formed on the substrate is then patterned into patterns for interconnections or electrodes, thereafter a passivation film is formed thereon to insulate and passivate the resulting interconnections or electrodes and to thus complete the semiconductor device.
Such metal and insulating films deposited on the underlying film under a reduced pressure or atmospheric pressure often have lower density or is not always sufficiently adhered to the underlying films. This becomes a cause of stress migration and electromigration, in particular, for fine interconnections, for instance, on the order of about 0.6 to 1.5 .mu.m and for thin interconnections, for instance, on the order of about 0.5 .mu.m, which occur as the degree of integration of LSI's increases. Accordingly, the density of films for interconnections, electrodes and insulating layers and the adhesion thereof to the underlying film greatly affect the yield of semiconductor devices and the reliability of the resulting interconnections. Therefore, this is an important problem to be solved in the fabrication of semiconductor devices.
For instance, it has been believed that the reduction in reliability of aluminum (Al) interconnections for IC's due to stress migration and electromigration results from low density of an Al film and insufficient adhesion thereof to an underlying film and a passivation film. It has likewise been believed that insufficient adhesion between a silicide layer and a polycrystalline silicon layer which constitute a two-layered structure (a polycide structure) used for forming interconnections and gate electrodes of semiconductor devices leads to peeling off or delaminating of the silicide film during a high temperature annealing process. It has been widely recognized that low-density insulating films cause corrosion of interconnections and instability of devices due to contaminants. These become a severe obstacle for the development of high quality semiconductor devices.
In general, a barrier layer of, for instance, titanium nitride is applied between Al interconnections and a silicon (si) substrate in order to prevent alloying reaction between Al and Si. The Si substrate and Al layers must be firmly adhered to such a barrier layer in order to obtain good barrier properties of the latter and lower contact resistance. For this reason, it is very important to develop a method for forming metal films having a high density and sufficient adhesion of the metal film to an underlying film for improving the yield of semiconductor devices and the reliability of interconnections.